Outgassing material coated cavity for a micro-electro mechanical system device and methods for forming the same

ABSTRACT

A MEMS support structure and a cap structure are provided. At least one vertically-extending trench is formed into the MEMS support structure or a portion of the cap structure. A vertically-extending outgassing material portion having a surface that is physically exposed to a respective vertically-extending cavity is formed in each of the at least one vertically-extending trench. A matrix material layer is attached to the MEMS support structure. A movable element laterally confined within a matrix layer is formed by patterning the matrix material layer. The matrix layer is bonded to the cap structure. A sealed chamber containing the movable element is formed. Each vertically-extending outgassing material portion has a surface that is physically exposed to the sealed chamber, and outgases a gas to increase the pressure in the sealed chamber.

RELATED APPLICATION

The instant application is a continuation of U.S. application Ser. No.16/784,451 filed on, Feb. 7, 2020, the entire contents of which areincorporated herein by reference.

BACKGROUND

Micro-electro mechanical system (MEMS) devices include devicesfabricated using semiconductor technology to form mechanical andelectrical features. MEMS devices may include moving parts havingdimensions of microns or sub-microns and a mechanism for electricallycoupling the moving parts to an electrical signal, which may be an inputsignal that induces movement of the moving parts or an output signalthat is generated by the movement of the moving parts. MEMS devices areuseful devices that may be integrated with other devices, such assemiconductor devices, to function as sensors or as actuators.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1A is a vertical cross-sectional view of a MEMS support structureafter formation of semiconductor devices such as field effecttransistors in accordance with a first embodiment of the presentdisclosure.

FIG. 1B is a vertical cross-sectional view of the MEMS support structureafter formation of interconnect-level dielectric material layers andmetal interconnect structures in accordance with the first embodiment ofthe present disclosure.

FIG. 1C is a vertical cross-sectional view of the MEMS support structureafter formation of an etch stop dielectric material layer and abonding-level dielectric material layer in accordance with the firstembodiment of the present disclosure.

FIG. 1D is a vertical cross-sectional view of the MEMS support structureafter formation of bonding-level metal interconnect structures inaccordance with the first embodiment of the present disclosure.

FIG. 1E is a vertical cross-sectional view of the MEMS support structureafter formation of recess regions in accordance with the firstembodiment of the present disclosure.

FIG. 1F is a vertical cross-sectional view of the MEMS support structureafter formation of vertically-extending trenches in accordance with thefirst embodiment of the present disclosure.

FIG. 1G is a vertical cross-sectional view of the MEMS support structureafter formation of an outgassing-material-containing layer in accordancewith the first embodiment of the present disclosure.

FIG. 1H is a vertical cross-sectional view of the MEMS support structureafter removal of a horizontally-extending portion of theoutgassing-material-containing layer in accordance with the firstembodiment of the present disclosure.

FIG. 1I is a vertical cross-sectional shape of an exemplary structurefor forming a MEMS device after formation of an assembly of the MEMSsupport structure and a matrix material layer in accordance with thefirst embodiment of the present disclosure

FIG. 1J is a vertical cross-sectional view of the exemplary structureafter thinning the matrix material layer in accordance with the firstembodiment of the present disclosure.

FIG. 1K is a vertical cross-sectional view of the exemplary structureafter patterning the matrix material layer into movable elements and amatrix layer in accordance with the first embodiment of the presentdisclosure.

FIG. 2A is a vertical cross-sectional view of an exemplary structure forforming a cap structure after formation of a bonding material layer inaccordance with the first embodiment of the present disclosure.

FIG. 2B is a vertical cross-sectional view of a cap structure afterformation of capping surfaces in accordance with the first embodiment ofthe present disclosure.

FIG. 3 is a vertical cross-sectional view of a first exemplarymicro-electro mechanical system (MEMS) device in accordance with thefirst embodiment of the present disclosure.

FIG. 4 is a vertical cross-sectional view of a second exemplary MEMSdevice in accordance with a second embodiment of the present disclosure.

FIG. 5 is a vertical cross-sectional view of a third exemplary MEMSdevice in accordance with a third embodiment of the present disclosure.

FIG. 6A is a vertical cross-sectional view of a first exemplaryconfiguration of a fourth exemplary MEMS device in accordance with afourth embodiment of the present disclosure.

FIG. 6B is a vertical cross-sectional view of a second exemplaryconfiguration of a fourth exemplary MEMS device in accordance with thefourth embodiment of the present disclosure.

FIGS. 7A-7C illustrate various horizontal cross-sectional views ofvertically-extending trenches that may be used in any of the embodimentsof the present disclosure.

FIG. 8A is a vertical cross-sectional view of a first exemplaryconfiguration of a fifth exemplary MEMS device in accordance with afifth embodiment of the present disclosure.

FIG. 8B is a vertical cross-sectional view of a second exemplaryconfiguration of a fifth exemplary MEMS device in accordance with thefifth embodiment of the present disclosure.

FIG. 9A is a vertical cross-sectional view of a first exemplaryconfiguration of a sixth exemplary MEMS device in accordance with asixth embodiment of the present disclosure.

FIG. 9B is a horizontal cross-sectional view of the sixth exemplary MEMSdevice at the level of the matrix layer of FIG. 9A.

FIG. 10 is a vertical cross-sectional view of a seventh exemplary MEMSdevice in accordance with the seventh embodiment of the presentdisclosure.

FIG. 11 is a vertical cross-sectional view of an exemplary structure forforming a MEMS assembly in accordance with a eighth embodiment of thepresent disclosure.

FIG. 12A is a vertical cross-sectional view of an exemplary structurefor forming a cap structure after formation of a bonding material layerin accordance with the eighth embodiment of the present disclosure.

FIG. 12B is a vertical cross-sectional view of an exemplary structurefor forming the cap structure after formation of vertically-extendingtrenches in accordance with the eighth embodiment of the presentdisclosure.

FIG. 12C is a vertical cross-sectional view of an exemplary structurefor forming the cap structure after formation of anoutgassing-material-containing layer in accordance with the eighthembodiment of the present disclosure.

FIG. 12D is a vertical cross-sectional view of the exemplary structurefor forming the cap structure after formation ofoutgassing-material-containing portions in accordance with the eighthembodiment of the present disclosure.

FIG. 12E is a vertical cross-sectional view of a cap structure inaccordance with the eighth embodiment of the present disclosure.

FIG. 13 is a vertical cross-sectional view of a eighth exemplary MEMSdevice in accordance with the eighth embodiment of the presentdisclosure.

FIG. 14 is a flow chart illustrating a set of processing steps that maybe performed to form a MEMS device according to embodiments of thepresent disclosure.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

Embodiments of the present disclosure are directed to micro-electromechanical system (MEMS) device containingoutgassing-material-containing portions located in vertically-extendingcavities configured to release gas into a sealed chamber and method forforming the same. Some MEMS devices may include a sealed chambercontaining a movable element. For example, the MEMS device may include amoving plate (i.e., movable elements) or sensing element that registersthe acceleration of the device or angular velocity of the device. Theoptimal condition for operation of the movable element may include agaseous ambient, which can be provided by including a gas sourceconnected to the sealed chamber. Various embodiments described hereinprovide an increased gas supply into sealed chambers by usingvertically-extending trenches that contain outgassing material portionswith physically exposed surfaces. The vertically extending trenches mayprovide an increased surface area from which the gas supply may emanate.An increase in the pressure of a gas ambient can provide enhancedperformance for some types of MEMS devices, such as an accelerometer.

Referring to FIG. 1A, an exemplary structure for forming a MEMS assemblyin accordance with a first embodiment of the present disclosure isillustrated. The exemplary structure includes a substrate. At least onemicro-electro mechanical system (MEMS) device may be subsequently formedon the substrate. For this reason, the substrate is herein referred toas a micro-electro mechanical system substrate, or a MEMS substrate 50.The MEMS substrate 50 may have a thickness in a range from 30 microns to3 mm, such as from 100 microns to 1 mm, although lesser and greaterthicknesses may also be used. The MEMS substrate 50 may be asemiconductor substrate, a conductive substrate, an insulatingsubstrate, or a composite substrate including multiple layers. In oneembodiment, the MEMS substrate 50 may be a semiconductor substrate suchas a commercially available single crystalline silicon wafer having adiameter in a range from 150 mm to 450 mm and having a thickness in arange from 500 microns to 1,000 microns.

In an embodiment the MEMS substrate 50 includes a semiconductorsubstrate, semiconductor devices 80 may be formed on a top surface ofthe MEMS substrate 50. The semiconductor devices 80 that may be formedon the top surface of the MEMS substrate 50 include, but are not limitedto, field effect transistors, bipolar transistors, diodes, capacitors,resistors, or other semiconductor devices known in the art. In anembodiment, the semiconductor devices 80 include field effecttransistors, each field effect transistor may include active regions 82(such as source regions and drain regions), a gate dielectric 85, and agate electrode 86. Shallow trench isolation structures 52 or othersuitable isolation structures may be formed between neighboring devices.The shallow trench isolation structures 52 may provide electricalisolation between the various semiconductor devices 80 on the MEMSsubstrate 50. The semiconductor devices 80 may comprise a circuitconfigured to interface with, control, and/or sense various componentswith the at least one MEMS device to be subsequently formed thereabove.

The combination of the MEMS substrate 50 and a set of structures formedthereupon, and/or to be subsequently formed thereupon, providesstructural support to the at least one micro-electro mechanical system(MEMS) device to be subsequently formed. In other words, the combinationof the MEMS substrate 50 and the set of material portions to be formedthereupon functions as a support structure for the at least one MEMSdevice. As such, the combination of the MEMS substrate 50 and the set ofmaterial portions formed thereupon, or to be formed thereupon, ishereafter referred to as a micro-electro mechanical system supportstructure 500, or a MEMS support structure 500. The exemplary structureincludes a first device region 101 in which a first MEMS device is to besubsequently formed, and a second device region 102 in which a secondMEMS device is to be subsequently formed. In a non-limiting illustrativeexample, components for an accelerometer for measuring linearacceleration may be formed in the first device region 101 and agyroscope for measuring angular velocity may be formed in the seconddevice region 102. In other non-limiting embodiments, a structure may beformed with repetitive first device regions 101 or second device regions102 to form a plurality of the same type of sensor.

Referring to FIG. 1B, interconnect-level dielectric material layers 20and metal interconnect structures 22 may be formed over thesemiconductor devices 80. The interconnect-level dielectric materiallayers 20 may include multiple dielectric material layers that arevertically stacked to accommodate metal interconnect structures 22 thatmay be formed at different metal interconnect levels. Each of theinterconnect-level dielectric material layers 20 may include adielectric material such as silicon oxide, silicon nitride,organosilicate glass, a porous low-k dielectric material, or a spin-onglass (SOG) material. Other suitable materials within the contemplatedscope of disclosure may also be used. The interconnect-level dielectricmaterial layers 20 may be deposited by chemical vapor deposition,physical vapor deposition, or spin-on coating. The thickness of eachinterconnect-level dielectric material layer 20 can be in a range from100 nm to 600 nm, although lesser and greater thicknesses can also beused. The metal interconnect structures 22 may include various metal viastructures and various metal line structures that provide electricalconnection among the various semiconductor devices 80 and among variousnodes of the semiconductor devices 80 and nodes of MEMS devices to besubsequently formed. In one embodiment, at least portion of the firstdevice region 101 may be free of metal interconnect structures 22 sothat vertically-extending trenches can be subsequently formed therein.

Referring to FIG. 1C, an etch stop dielectric material layer 30 may beformed over the interconnect-level dielectric material layers 20. Theetch stop dielectric material layer 30 can include silicon nitride or adielectric metal oxide (such as aluminum oxide), and can have athickness in a range from 30 nm to 100 nm, although lesser and greaterthicknesses can also be employed. A bonding-level dielectric materiallayer 34 may be formed over the etch stop dielectric material layer 30.The bonding-level dielectric material layer 34 may include silicon oxidesuch as TEOS oxide, which is an oxide material formed by decompositionof tetraethylorthosilicate (TEOS). The thickness of the bonding-leveldielectric material layer 34 may be in a range from 200 nm to 3,000 nm,although lesser and greater thicknesses can also be employed.

Referring to FIG. 1D, bonding-level metal interconnect structures 32 maybe formed in the bonding-level dielectric material layer 34 and the etchstop dielectric material layer 30. The bonding-level metal interconnectstructures 32 may include metal line structures, metal via structures,or a combination thereof (such as integrated line and via structures).For example, via cavities, line cavities, and/or pad cavities can beformed in the bonding-level dielectric material layer 34 and the etchstop dielectric material layer 30, and may be filled with at least onemetallic fill material to form the bonding-level metal interconnectstructures 32.

Referring to FIG. 1E, recess region 37 may be formed by verticallyrecessing portions of the top surface of the bonding-level dielectricmaterial layer 34. The top surface of the etch stop dielectric materiallayer 30 may be employed as an etch stop surface. The recess regions 37may be formed in areas in which movable elements of MEMS devices may besubsequently formed. The lateral extent of each recess region 37 is onthe order of the lateral extent of a respective movable element that maybe subsequently formed, and may be in a range from 10 microns to 5 mm,although lesser and greater dimensions may also be employed. Each recessregion 37 may have a respective horizontal bottom surface, which may bethe top surface of the etch stop dielectric material layer 30.

Referring to FIG. 1F, a photoresist layer (not shown) may be appliedover the physically exposed surface of the etch stop dielectric materiallayer 30, the bonding-level dielectric material layer 34, and thebonding-level metal interconnect structures 32. The photoresist layermay be lithographically patterned to form at least one opening withinthe area of the first device region 101. An anisotropic etch process maybe performed using the patterned photoresist layer to formvertically-extending trenches 69. The vertically extending trenches 69may vertically extend through the etch stop dielectric material layer 30and into at least one of the interconnect-level dielectric materiallayers 20. Each vertically-extending trench 69 may have a bottom surfacewithin one of the interconnect-level dielectric material layers 20.Alternatively, each vertically-extending trench 69 may extend into theMEMS substrate 50 (through shallow trench isolation structures 52), andhave a bottom surface within the MEMS substrate 50. The at least onevertically-extending trench 69 may include a plurality ofvertically-extending trenches. While FIG. 1F depict two verticallyextending trenches 69 for illustrative purposes, additional verticallyextending trenches 69 are contemplated within the scope of thisdisclosure.

Each vertically-extending trench 69 can have a respective width w at atopmost portion, i.e., at a periphery that adjoins the top surface ofthe etch stop dielectric material layer 30. The width w can be measuredbetween top edges of opposing segments of the sidewalls for eachvertically-extending trench 69 that face each other. The width w may beuniform throughout a vertically-extending trench 69, for example, for avertically-extending trench 69 having a rectangular opening or for avertically-extending trench having an inner sidewall and an outersidewall located on a respective arc of two concentric circles havingdifferent radii. Alternatively, one or more of the at least onevertically-extending trench 69 can have a width modulation. For example,the maximum width of a vertically-extending trench 69 having a widthmodulation may be the width w, and the vertically-extending trench 69can include at least one region having a lesser width than the width w.

Further, each vertically-extending trench 69 can have a respective depthd between a top periphery and a bottom surface. For eachvertically-extending trench 69, the depth d can be at least twice thewidth w. In one embodiment, the aspect ratio of eachvertically-extending trench 69, i.e., the ratio of the depth d to thewidth w, can be in a range from 2 to 40 (i.e., the depth d twice thewidth w to the depth d being 40 times the width w), such as from 3 to10. In one embodiment, each vertically-extending trench 69 can havestraight sidewalls. In such an embodiment, the straight sidewalls ofeach vertically-extending trench 69 may be vertical, or may have a taperangle greater than 0 degree and less than 45 degrees, such as between 0degree and 10 degrees. Alternatively, the sidewalls of thevertically-extending trench 69 may be convex or concave with a generallydecreasing width with an increasing distance from the horizontal planeincluding the top surface of the etch stop dielectric material layer 30.In a non-limiting illustrative example, each vertically-extending trench69 can have a width w in a range from 150 nm to 5,000 nm, and a depth ina range from 300 nm to 10,000 nm, although lesser and greater dimensionscan also be used. The aspect ratio of each vertically-extending trench69 can be in a range from 1.0 to 60, such as from 1.5 to 10.

Referring to FIG. 1G, an outgassing-material-containing layer 62L may bedeposited in each vertically-extending trench 69 and over the topsurface of the etch stop dielectric material layer 30. Theoutgassing-material-containing layer 62L includes at least onecontinuous layer that contains an outgassing material that is hereinreferred to as at least one continuous outgassing material layer. Theoutgassing-material-containing layer 62L may consist of the at least onecontinuous outgassing material layer in some embodiments, or may includeat least one additional material layer in some other embodiments to besubsequently described. In one embodiment, theoutgassing-material-containing layer 62L may consist of a singlecontinuous outgassing material layer or a stack of multiple continuousoutgassing material layers.

Each continuous outgassing material layer within theoutgassing-material-containing layer 62L includes an outgassing materialthat is capable of outgassing at a temperature above room temperature.In an illustrative example, the outgassing-material-containing layer 62Lcan include a continuous outgassing material layer contacting a siliconoxide material deposited using a silicon oxide deposition process thatsubsequently outgasses. Various types of silicon oxide materials can bedeposited employing such deposition processes as sputtering (physicalvapor deposition), plasma-enhanced chemical vapor deposition, highdensity plasma chemical vapor deposition, and thermal silicon oxidedeposition. The lateral thickness t of each vertical portion of theoutgassing-material-containing layer 62L at an opening of a respectivevertically-extending trench 69 is less than one half of the width w ofthe respective vertically-extending trench 69. For example, the lateralthickness t of each vertical portion of theoutgassing-material-containing layer 62L can be in a range from 50 nm to2,500 nm, although lesser and greater lateral thicknesses can also beused. Generally, the lateral thickness t of each vertical portion of theoutgassing-material-containing layer 62L is thick enough to contain asignificant amount of the outgassing material (e.g., by being greaterthan 50 nm), and is thin enough to enable deposition by commerciallyavailable film deposition techniques such as chemical vapor deposition(e.g., by being less than 2,500 nm). A vertically-extending cavity 69′is present within a center region of each vertically-extending trench69. Thus, each vertically-extending portion of theoutgassing-material-containing layer 62L can be physically exposed to arespective vertically-extending trench 69. Each physically exposedsurface of a vertically-extending portion of theoutgassing-material-containing layer 62L can include avertically-extending surface, i.e., a surface that extends along avertical direction, and may have a straight sidewall, a concavesidewall, or a convex sidewall. If a physically exposed surface of avertically-extending portion of the outgassing-material-containing layer62L has a straight sidewall, the straight sidewall may be vertical ortapered.

The gas content and the outgassing rate of the silicon oxide materialcan be adjusted by changing parameters of the deposition process such aschamber pressure, gas flow rates, and radio-frequency (RF) power.Alternatively, the outgassing-material-containing layer 62L can becomposited of any material capable of outgassing, such as, but notlimited to, polyimide, poly (para-xylylene) derivatives, and otherorganic compounds. In one embodiment, the outgassing-material-containinglayer 62L may comprise, and/or may consist of, a plurality of materiallayers in which at least one material layer is capable of outgassing.

Deposition processes for depositing the outgassing-material-containinglayer 62L include, but are not limited to, plasma-enhanced chemicalvapor deposition (PECVD), high density plasma chemical vapor deposition(HDPCVD), low pressure chemical vapor deposition (LPCVD), magnetronsputtering, thermal evaporation, e-beam evaporation, and atomic layerdeposition (ALD).

Referring to FIG. 1H, the horizontal portion of theoutgassing-material-containing layer 62L that overlies the horizontalsurface including the top surface of the etch stop dielectric materiallayer 30 may be removed by a planarization process. For example, ananisotropic etch process may be performed to remove the horizontalportion of the outgassing-material-containing layer 62L that overliesthe horizontal surface including the top surface of the etch stopdielectric material layer 30. Optionally, a patterned photoresist layer(not shown) may be employed to cover the areas including thevertically-extending trenches 69 during the anisotropic etch process.The photoresist layer may be subsequently removed, for example, byashing. Each remaining portion of the outgassing-material-containinglayer 62L located within a respective vertically-extending trench 69constitutes an outgassing-material-containing portion 62.

Generally, a horizontal portion of a continuous outgassing materiallayer within the outgassing-material-containing layer 62L may be removedoutside the region including the at least one vertically-extendingtrench 69. The horizontal portion of a continuous outgassing materiallayer within the outgassing-material-containing layer 62L can be removedby an anisotropic etch process that does not use any etch mask layer, oran anisotropic etch process that uses a patterned photoresist layer thatcovers the region including the at least one vertically-extending trench69. In one embodiment, the outgassing-material-containing layer 62L maybe entirely removed from above the horizontal plane including the topsurface of the etch stop dielectric material layer 30, or only outsidethe area that is not covered by the patterned photoresist layer. If apatterned photoresist layer is used, the patterned photoresist layer cancontinuously extend over the entire area of the at least onevertically-extending trench 69.

Each outgassing-material-containing portion 62 can include avertically-extending outgassing material portion having avertically-extending surface. Each vertically-extending surface of theoutgassing-material-containing portions 62 may have a straight sidewall,a concave sidewall, or a convex sidewall. If anoutgassing-material-containing portion 62 has a straight sidewall, thestraight sidewall may be vertical or tapered. Each vertically-extendingsurface of the vertically-extending outgassing material portion can bephysically exposed to, and thus, can be in contact with, a respectivevertically-extending cavity 69′ that is located in a respectivevertically-extending trench 69.

An upper periphery of each vertically-extending outer sidewall of theoutgassing-material-containing portion 62 can be adjoined to a samehorizontal surface, which is herein referred to as a horizontalreference surface. In one embodiment, the horizontal reference surfacecan be a top horizontal surface of the etch stop dielectric materiallayer 30. In one embodiment, each vertically-extending outgassingmaterial portion of the outgassing-material-containing portion 62 canhave a vertical extent that is greater than a lateral dimension, such asthe width w, of the respective one of the at least onevertically-extending trench 69 at a level of the reference horizontalplane. In one embodiment, each vertically-extending outgassing materialportion of the outgassing-material-containing portion 62 can have alateral thickness t that is less than one half of the lateral dimension,such as the width w, of the respective one of the at least onevertically-extending trench 69.

Referring to FIG. 1I, a matrix material layer 10L may be provided. Thematrix material layer 10L may include a semiconductor material, whichmay be silicon, germanium, a silicon-germanium alloy, a compoundsemiconductor material that can be doped to locally alter electricalconductivity, or any other semiconductor material. In one embodiment,the matrix material layer 10L may have a thickness in a range from 30microns to 1 mm, although lesser and greater thicknesses can also beused. In one embodiment, the matrix material layer 10L may include ahydrogen-implanted layer to provide subsequent cleaving of the matrixmaterial layer 10L. In such an embodiment, the depth of thehydrogen-implanted layer from a major surface of the matrix materiallayer 10L may be in a range from 100 nm to 3 microns, such as from 300nm to 1,000 nm, although lesser and greater depths can also be used.

The matrix material layer 10L may attached to the MEMS support structure500. In one embodiment, the matrix material layer 10L may be bonded tothe bonding-level dielectric material layer 34 of the MEMS supportstructure 500, for example, by oxide-to-semiconductor bonding. Forexample, the matrix material layer 10L may be pressed against the topsurface of the bonding-level dielectric material layer 34, and may beannealed at a temperature in a range from 150 degrees Celsius to 400degrees Celsius to induce bonding between the bonding-level dielectricmaterial layer 34 and the matrix material layer 10L. A bonded assemblyof a MEMS support structure 500 and the matrix material layer 10L may beformed. Laterally-extending cavities 39 may be formed between the etchstop dielectric material layer 30 and the matrix material layer 10L.Each of the vertically-extending cavities 69′ may be connected to arespective one of the laterally-extending cavities 39.

Referring to FIG. 1J, the matrix material layer 10L may be thinned toprovide a thinned matrix material layer 10T. The thickness of thethinned matrix material layer 10T may be in a range from 100 nm to 50microns, such as from 2 microns to 20 microns, although lesser andgreater thicknesses can also be used. In one embodiment, the thinning ofthe matrix material layer 10L may be performed by grinding, polishing,an isotropic etch process, an anisotropic etch process, or a combinationthereof. In embodiments in which a hydrogen-implanted layer may beprovided within the matrix material layer 10L, a cleaving process may beused to remove distal portions of the matrix material layer 10L that aremore distal from the MEMS substrate 50 than the hydrogen-implantedlayer. In embodiments in which a cleaving process is employed, an annealat an elevated process in a range from 400 degrees Celsius to 600degrees Celsius may be performed for the cleaving process to inducebubbling of hydrogen atoms at the level of the hydrogen-implanted layerwithin the matrix material layer 10L. Generally, a matrix material layerincluding a semiconductor material, such as the thinned matrix materiallayer 10T, can be formed over the MEMS support structure 500.

Referring to FIG. 1K, a photoresist layer (not shown) may be appliedover the thinned matrix material layer 10T, and may be lithographicallypatterned to form openings in areas that define gaps 19 between movableelements and a matrix layer to be subsequently patterned from thethinned matrix material layer 10T. In other words, the pattern of theopenings in the photoresist layer may include the pattern of the gaps 19between the movable elements and the matrix layer to be subsequentlypatterned from the thinned matrix material layer 10T.

An anisotropic etch process may be performed to transfer the pattern ofthe opening in the photoresist layer through the thinned matrix materiallayer 10T. The thinned matrix material layer 10T may be divided intomultiple portions, which include movable elements (10 a, 10 b) and amatrix layer 10 that laterally surrounds each of the movable elements(10 a, 10 b). Generally, the movable elements (10 a, 10 b) may includeany element that is capable of bending, vibrating, deforming,displacement, rotating, twisting, and any other type of change in shape,position, and/or orientation. In an illustrative example, the movableelements (10 a, 10 b) may include a first movable element 10 a formed inthe first device region 101 and a second movable element 10 b formed inthe second device region 102. For example, the first movable element 10a may be used for an accelerometer, and the second movable element 10 bmay be used for a gyroscope. Generally, a first movable element 10 a maybe configured to operate at higher ambient pressure than the secondmovable element 10 b. In other words, the optimal operating pressure forthe MEMS device including the first movable element 10 a may be higherthan the optimal operating pressure for the MEMS device including thesecond movable element 10 b.

According to an aspect of the present disclosure, thevertically-extending trenches 69 and the outgassing-material-containingportions 62 may be formed only in the area of the first device region101, and not formed in the area of the second device region 102.According to another aspect of the present disclosure, thevertically-extending trenches 69 and the outgassing-material-containingportions 62 may be formed in the area of the first device region 101 ata higher areal density than in the area of the second device region 102.

Additional movable elements (not shown) may be patterned out of thethinned matrix material layer 10T. A continuous remaining portion of thethinned matrix material layer 10T that laterally surrounds each of themovable elements (10 a, 10 b) constitutes a stationary portion of MEMSdevices against which relative movement of the movable elements (10 a,10 b) may be measured. The stationary remaining portion of the MEMSdevices is herein referred to as a matrix layer 10. The movable elements(10 a, 10 b) and the matrix layer 10 may include a same material. In oneembodiment, the movable elements (10 a, 10 b) and the matrix layer 10may include a same semiconductor material, which is herein referred toas the first semiconductor material. A subset and/or portions of themovable elements (10 a, 10 b) may be doped with p-type dopants and/orn-type dopants as needed. Gaps 19 extending down to thelaterally-extending cavities 39 may formed between the matrix layer 10and the various movable elements (10 a, 10 b).

The movable elements (10 a, 10 b) may be detached from the matrix layer10 by the gaps 19. A MEMS assembly is provided, which may include theMEMS support structure 500, the matrix layer 10, and at least onemovable element (10 a, 10 b) laterally confined by the matrix layer 10.The MEMS support structure 500 includes the MEMS substrate 50,interconnect-level dielectric material layers 20 located between theMEMS substrate 50 and the matrix layer 10 and having metal interconnectstructures 22 formed within the dielectric material layer 20, an etchstop dielectric material layer 30, a bonding-level dielectric materiallayer 34, bonding-level metal interconnect structures 32, andoutgassing-material-containing portions 62 located withinvertically-extending trenches 69. Generally, at least one movableelement (10 a, 10 b) may be laterally confined within the matrix layer10 that overlies the MEMS support structure 500.Outgassing-material-containing portions 62 may be formed in the MEMSsupport structure 500 between the matrix layer 10 and the MEMS substrate50. The structure illustrated in FIG. 1K includes a MEMS assembly, whichcan be subsequently bonded to a cap structure to form a MEMS device.

Referring to FIG. 2A, a cap structure 700 is illustrated, which can besubsequently bonded to the matrix layer 10 of FIG. 1K upon furtherpatterning. The cap structure 700 includes a substrate, which is hereinreferred to as a cap substrate 70. The cap substrate 70 may include asemiconductor material, an insulating material, and/or a conductivematerial. In one embodiment, the cap substrate 70 may include asemiconductor material, which is herein referred to as a secondsemiconductor material. For example, the cap substrate 70 may include asilicon substrate. The thickness of the cap substrate 70 may be in arange from 60 microns to 1 mm, although lesser and greater thicknessescan also be used. Optionally, complementary metal-oxide-semiconductor(CMOS) devices such as field effect transistors (not shown) can beprovided on the backside of the cap structure 700.

The cap structure 700 may have multiple device regions arranged in amirror image pattern of the pattern of the various device regions (101,102) of the MEMS assembly illustrated in FIG. 1K. For example, the capstructure 700 may include a first device region 201, a second deviceregion 202, and optional additional device regions (not illustrated).The first device region 201 of the cap structure 700 may have a mirrorimage shape of the first device region 101 of the MEMS assembly of FIG.1K, and the second device region 202 of the cap structure 700 can have amirror image shape of the second device region 102 of the second deviceregion 102 of the MEMS assembly of FIG. 1K.

A bonding material may be deposited on the top side of the cap substrate70 to form a bonding material layer 72. The bonding material of thebonding material layer 72 can include any material that can bond withthe semiconductor material of the matrix layer 10. For example, thebonding material layer 72 can include silicon oxide that can formsilicon-silicon oxide bonding with the semiconductor material of thematrix layer 10, a metallic material such as aluminum, analuminum-silicon alloy, or an aluminum-germanium alloy that can formeutectic bonding with the semiconductor material of the matrix layer 10,or any other adhesive material that can form a vacuum-tight seal withthe semiconductor material of the matrix layer 10. Alternatively, asurface portion of the thinned matrix material layer 10T may be oxidizedby a plasma oxidation process after the processing steps of FIG. 1J andprior to the processing steps of FIG. 1K to provide silicon oxidesurface portions on top of each of the movable elements (10 a, 10 b) andon top of the matrix layer 10, and the bonding material layer 72 caninclude silicon oxide that is subsequently used for siliconoxide-silicon oxide bonding with the silicon oxide surface layeroverlying the matrix layer 10.

In one embodiment, the bonding material layer 72 may include siliconoxide and may have a thickness in a range from 30 nm to 300 nm, althoughlesser and greater thicknesses can also be used. The bonding materiallayer 72 may be conformally or non-conformally deposited. For example,the bonding material layer 72 may include undoped silicate glass formedby decomposition of tetraethylorthosilicate. In another embodiment, thebonding material layer 72 can include aluminum, an aluminum-siliconalloy, or an aluminum-germanium alloy having a thickness in a range from20 nm to 200 nm, although lesser and greater thicknesses can also beused.

Referring to FIG. 2B, the top surface of the cap structure 700 can bepatterned using at least one combination of a lithographic patterningprocess and an etch process. In each lithographic patterning process, aphotoresist layer is applied over a top surface of the cap structure700, and is lithographically exposed and developed to form a patternedphotoresist layer that functions as an etch mask layer. In each etchprocess, unmasked surface portions of the cap structure 700 are removedusing the patterned photoresist layer as an etch mask layer. The etchprocess can include an isotropic etch process (such as a wet etchprocess) or an anisotropic etch process (such as a reactive ion etchprocess). The duration of the etch process can be selected to controlthe depth of the recesses formed by the etch process. The photoresistlayer can be removed after the etch process, for example, by ashing.

A first recess region 177 having a first recessed surface can be formedin the first device region 201, and a second recess region 277 having asecond recessed surface can be formed in the second device region 202.The first recessed surface is subsequently used as a first cappingsurface for the first movable element 10 a, and the second recessedsurface is subsequently used as a second capping surface for the secondmovable element 10 b. Multiple combination of a lithographic patterningprocess and an etch process can be performed to provide various recessedsurfaces having different depth across various device regions. Forexample, a recessed surface in the first device region 201 may have adifferent recess depth than a recessed surface in the second deviceregion 202. Further, at least one of the recessed surfaces may havesteps to provide a pattern in a respective recessed surface. The patternand the depth of each recessed surface can be optimized for each MEMSdevice to be formed in the various device regions. The depths of therecessed surfaces, as measured from the top surface of the bondingmaterial layer 72, may be in a range from 50 nm to 50 microns, althoughlesser and greater depths can also be used.

Referring to FIG. 3, the cap structure 700 of FIG. 2B may be bonded tothe MEMS assembly of FIG. 1K to form an exemplary micro-electromechanical system (MEMS) device 300, which is herein referred to asfirst exemplary MEMS device 300. The first exemplary MEMS device 300 mayhave a first device region 301 and second device region 302. In thisillustrated embodiment, the cap structure 700 may be bonded to thematrix layer 10 such that the front side (i.e., the upside asillustrated in FIG. 2B) of the cap structure 700 faces the matrix layer10 (effectively flipping the cap structure 700 illustrated in FIG. 2Bupside down). In one embodiment, the bonding of the cap structure 700 tothe matrix layer 10 may be achieved by bonding the matrix layer 10 tothe bonding material layer 72. Depending on the material composition ofthe bonding material layer 72, the bonding may use silicon to siliconoxide bonding, eutectic bonding between a metal and the semiconductormaterial of the matrix layer 10, or silicon oxide to silicon oxidebonding (in which case a silicon oxide layer is provided on the topsurface of the matrix layer 10 and is bonded to the silicon oxidematerial of the bonding material layer 72).

A first sealed chamber 109 including a first movable element 10 a may beformed by aligning the first recess region of the cap structure 700 overthe first movable element 10 a during bonding the cap structure 700 tothe matrix layer 10. The first sealed chamber 109 includes a first headvolume that overlies the first movable element 10 a, and the secondsealed chamber 209 includes a second head volume that overlies thesecond movable element 10 b. The first sealed chamber 109 may belaterally bounded by the matrix layer 10 and may be vertically boundedby the first capping surface that overlies the first movable element 10a. A first MEMS device 100 includes the first movable element 10 a, thefirst sealed chamber 109, and the first capping surface. The first MEMSdevice 100 may form an accelerometer.

A second sealed chamber 209 including a second movable element 10 b maybe formed by aligning the second recess region of the cap structure 700over the second movable element 10 b during bonding the cap structure700 to the matrix layer 10. The second sealed chamber 209 may include asecond head volume that overlies the second movable element 10 b. Thesecond sealed chamber 209 may be vertically bounded by a second cappingsurface that overlies the second movable element 10 b. The secondcapping surface can comprise the planar horizontal surface of the capstructure 700 located within the second recess region. The second sealedchamber 209 may be vertically bounded by the second capping surface thatoverlies the second movable element 10 b. A second MEMS device 200includes the second movable element 10 b, the second sealed chamber 209,and the second capping surface. The MEMS device of the presentdisclosure can be a composite MEMS device including the first MEMSdevice 100 (which can include an accelerometer) and the second MEMSdevice 200 (which can include a gyroscope).

In one embodiment, the first sealed chamber 109 can be bounded by ahorizontal capping surface of the portion of the cap structure 700 thatfaces the matrix layer 10. Each vertically-extending outgassing materialportion of the outgassing-material-containing portions 62 can have asurface that is physically exposed to the first sealed chamber 109. Atleast one vertically-extending trench 69 extends into theinterconnect-level dielectric material layers 20, and includes arespective vertically-extending outgassing material portion having asurface in contact with (and thus, physically exposed to) a respectivevertically-extending cavity 69′. Each vertically-extending cavity 69′can be a portion of the first sealed chamber 109. In one embodiment,each vertically-extending outgassing material portion can have a surfacethat is physically exposed to the first sealed chamber 109. By includingthe at least one vertically-extending trench 69 withoutgassing-material-containing portions 62 formed on the sides in thefirst sealed chamber 109, but not in the second sealed chamber 209,different pressures in each of the chambers 109, 209 may be achieved.

In one embodiment, the interconnect-level dielectric material layers 20may be disposed between the MEMS substrate 50 and the matrix layer 10.Metal interconnect structures (22, 32) can be formed in theinterconnect-level dielectric material layers 20 and in thebonding-level dielectric material layer 34. In one embodiment, the atleast one vertically-extending trench 69 extends through at least one ofthe interconnect-level dielectric material layers 20. In one embodiment,each vertically-extending outgassing material portion is locatedentirely within a volume of a respective one of the at least onevertically-extending trench 69.

In one embodiment, a CMOS circuit that controls each of the first MEMSdevice 100 and the second MEMS device 200 can be provided among thesemiconductor devices 80 on the MEMS substrate 50. Alternatively, oradditionally, semiconductor devices that controls one of more of theMEMS devices (100, 200) may be provided in, or on, the cap structure70-.

Referring to FIG. 4, a second exemplary MEMS device 300 in accordancewith a second embodiment of the present disclosure is illustrated. Thesecond exemplary MEMS device can be derived from the first exemplaryMEMS device of FIG. 4 by modifying the depth d of the at least onevertically-extending trench 69, and thus, the vertical extent of eachoutgassing-material-containing portion 62. Specifically, the anisotropicetch process that forms the at least one vertically-extending trench 69can be modified so that the at least one vertically-extending trench 69vertically extends through each of the interconnect-level dielectricmaterial layers 20 and into an upper portion of the MEMS substrate 50.Each vertically-extending outgassing material portion of theoutgassing-material-containing portion 62 can be located entirely withina volume of a respective one of the at least one vertically-extendingtrench 69. In one embodiment, each outgassing-material-containingportion 62 in a vertically-extending trench 69 can be formed as a singlecontinuous material portion without any hole therethrough.

Referring to FIG. 5, a third exemplary MEMS device 300 in accordancewith a third embodiment of the present disclosure is illustrated. Thethird exemplary MEMS device 300 of the present disclosure can be derivedfrom the first exemplary MEMS device 300 or the second exemplary MEMSdevice of the present disclosure by patterning theoutgassing-material-containing layer 62L using a combination of alithographic patterning process and a pattern transfer process includingan etch process at the processing steps of FIG. 1H. Specifically, aphotoresist layer can be applied over the outgassing-material-containinglayer 62L, and can be lithographically patterned to remove horizontalportions of the outgassing-material-containing layer 62L located outsidethe region including the at least one vertically-extending trench 69.The remaining portion of the photoresist layer can extend over, and cancover each of, the at least one vertically-extending trench 69. The areacovered by the patterned photoresist layer can be entirely within thearea of the first device region 101. Portions of theoutgassing-material-containing layer 62L that are not covered by thepatterned photoresist layer may be removed by an etch process thatetches the material of the outgassing-material-containing layer 62Lselective to the material of the thinned matrix material layer 10T. Thephotoresist layer can be removed, for example, by ashing. Theoutgassing-material-containing portion 62 can be formed as a singlecontiguous material portion without any hole therethrough. If aplurality of vertically-extending trenches 69 are present, theoutgassing-material-containing portion 62 can include a plurality ofvertically-extending outgassing material portions that are adjoined to ahorizontally-extending outgassing material portion that contacts ahorizontal surface (i.e., a top surface) of the etch stop dielectricmaterial layer 30. The at least one vertically-extending outgassingmaterial portion of the third exemplary MEMS device 300 can include aportion of an outgassing-material-containing layer 62 that includes ahorizontally-extending portion contacting a horizontal surface of theetch stop dielectric material layer 30. In an alternative embodiment inwhich the at least one outgassing-material-containing portion 62 may beformed in the cap structure 700, the at least one vertically-extendingoutgassing material portion of the third exemplary MEMS device 300 caninclude a horizontally-extending portion contacting a horizontal surfaceof the portion of the cap structure 700 that faces the matrix layer 10.

Referring to FIGS. 6A and 6B, configurations of a fourth exemplary MEMSdevice in accordance with a fourth embodiment of the present disclosureare illustrated. In such an embodiment, the sidewalls of eachvertically-extending trench 69 can include at least one tapered surfaceas illustrated in FIG. 6A, and/or at least one retro-tapered and/orconcave surface as illustrated in FIG. 6B. A tapered surface of avertically-extending trench 69 can be formed by performing ananisotropic etch process that induces polymerization of a photoresistmaterial in a patterned photoresist layer and coating of sidewalls ofthe vertically-extending trenches 69 under formation by the polymerizedphotoresist material during the anisotropic etch process at theprocessing step of 1G. In an embodiment, the configuration illustratedin FIG. 6A can be provided. Alternatively, a vertically-extending trench69 including retro-tapered surfaces and/or having a bottle shape can beformed by performing a series of processing steps in lieu of theanisotropic etch process of FIG. 1F. For example, the materials of theinterconnect-level dielectric material layers 20 may be etched selectiveto the material of the etch stop dielectric material layer 30 after theprocessing steps of FIG. 1F. In such an embodiment, the materials of theinterconnect-level dielectric material layers 20 may be isotropicallyetched by providing at least one isotropic etchant through the upperportion of the vertically-extending trench 69. The vertically-extendingtrench 69 can be laterally expanded to provide a bottle-shaped profileand/or the retro-tapered surfaces illustrated in FIG. 6B.

Referring to FIGS. 7A-7C illustrate various horizontal cross-sectionalviews (which can be the same as a respective top-down view) ofvertically-extending trenches 69 that may be used in any of theembodiments of the present disclosure. In some embodiments, thevertically-extending cavities 69 may have an annular rectangular shapeor any other polygonal or curvilinear annular shape as illustrated inFIG. 7A. In some embodiments, the vertically-extending cavities 69 mayhave a non-annular polygonal or generally curvilinear shape having arespective single periphery as illustrated in FIGS. 7B and 7B. The widthw illustrated in FIG. 1F can correspond to a lateral distance betweeneach facing pair of sidewall segments. For example, the width willustrated in FIG. 1F may correspond to a lateral separation distancebetween lengthwise sidewalls of a rectangular portion of a shape, or adiameter of a circle. In embodiments in which a facing pair of sidewallsegments is absent, such as in embodiments of a triangular shape, thewidth w illustrated in FIG. 1F may be defined between a straightsidewall and a distal apex of a polygon. Generally, the lateralthickness of each outgassing-material-containing portion 62 can becontrolled such that a vertically-extending cavity 69′ is formed withineach vertically-extending trench 69 at the processing steps of FIG. 1H.

Referring to FIG. 8A, a first exemplary configuration of a fifthexemplary MEMS device 300 in accordance with a fifth embodiment of thepresent disclosure is illustrated. The first exemplary MEMS device 300can be derived from any of the first through fourth MEMS devices 300described above by depositing a plurality of layers for theoutgassing-material-containing layer 62L. For example, theoutgassing-material-containing layer 62L can be formed by sequentiallydepositing an outgassing material layer 622, an adhesion promotionmaterial layer 623, and a hydrophobic coating layer 624. The outgassingmaterial layer 622 includes an outgassing material such as silicon oxideformed by high density plasma chemical vapor deposition process or anyof the other outgassing materials described above. Other suitablematerials that are within the contemplated scope of disclosure.

The adhesion promotion material layer 623 includes a material thatprovides enhanced adhesion of the material of the hydrophobic coatinglayer 624 to the outgassing material layer 622. The adhesion promotionmaterial layer 623 prevents peeling off of the outgassing material layer622, and thus, prevents particulate generation and blockage of movementof a movable element in an encapsulated cavity. In an illustrativeexample, the adhesion promotion material layer 623 can include a siliconoxide material having a different material composition than the materialof the outgassing material layer 622 and provides a continuous siliconoxide surface that functions as a better nucleation surface for thematerial of the hydrophobic coating layer 624. For example, the adhesionpromotion material layer 623 can include silicon oxide formed by plasmaenhanced chemical vapor deposition process or by an atomic layerdeposition process. The thickness of the adhesion promotion materiallayer 623 can be in a range from 1 nm to 20 nm, although lesser andgreater thicknesses can also be used. In an embodiment, the adhesionpromotion material layer 623 may be thick enough, e.g., greater than 1nm in thickness, to form a continuous material layer, and may be thinenough, e.g., less than 20 nm, to minimize the volume occupied by theadhesion promotion material layer 623 and to provide more space for theoutgassing material layer.

The hydrophobic coating layer 624 can include a material providing ahydrophobic surface. In one embodiment, the hydrophobic coating layer624 can include, and/or can consist essentially of, a self-assemblypolymer material having a hydrophobic functional group that isphysically exposed to the ambient. In one embodiment, the hydrophobiccoating layer 624 can include a self-assembly polymer material that canbe coated on the surface of the adhesion promotion material layer 623.For example, organosilane precursors such as CF₃(CF₂)₅(CH₂)₂SiCl₃(FOTS), CF₃(CF₂)₅(CH₂)₂Si(OC₂H₅)₃ (FOTES), CF₃(CF₂)₅(CH₂)₂Si(CH₃)Cl₂(FOMDS), CF₃(CF₂)₅(CH₂)₂Si(CH₃)₂Cl (FOMMS), CF₃(CF₂)₇(CH₂)₂SiCl₃ (FDTS),or CH₃(CH₂)₁₇(CH₂)₂SiCl₃ (OTS). Other suitable materials that are withinthe contemplated scope of disclosure. Processes for forming a layer of aself-assembly polymer material having a physically exposed hydrophobicfunctional group is known, for example, in Zhuang et al., Vapor-PhaseSelf-Assembled Monolayers for Anti-Stiction Applications in MEMS,Journal of Microelectromechanical Systems 16(6): 1451-1460, January2008.

The hydrophobic coating layer 624 and the adhesion promotion materiallayer 623 can be patterned concurrently with patterning of theoutgassing material layer 622 at the processing steps of FIG. 1H or anyequivalent processing steps for patterning theoutgassing-material-containing layer 62L. The first exemplaryconfiguration of the fifth exemplary MEMS device 300 can include anadhesion promotion material layer 623 over each portion (including eachvertically-extending outgassing material portion) of the outgassingmaterial layer 622, and a hydrophobic coating layer 624 located on theadhesion promotion material layer 623. In such an embodiment, eachvertically-extending outgassing material portion (comprising anoutgassing material layer 622) within an outgassing-material-containingportion 62 can contact a respective adhesion promotion material layer623, which contacts a respective hydrophobic coating layer 624.

Referring to FIG. 8B, a second exemplary configuration of the fifthexemplary MEMS device 300 can be derived from the first exemplaryconfiguration of the fifth exemplary MEMS device 300 by using a gluematerial layer 621 to enhance adhesion of the outgassing material layer622 to the matrix layer 10 and/or to the interconnect-level dielectricmaterial layers 20. In one embodiment, the glue material layer 621 caninclude a silicon oxide material including less gas than the outgassingmaterial layer 622. For example, the glue material layer 621 can includesilicon oxide formed by plasma enhanced chemical vapor depositionprocess or by an atomic layer deposition process. The thickness of theglue material layer 621 can be in a range from 3 nm to 60 nm, althoughlesser and greater thicknesses can also be used. In such an embodiment,each vertically-extending outgassing material portion (comprising anoutgassing material layer 622) within an outgassing-material-containingportion 62 can be attached to the matrix layer 10 through a respectiveglue material layer 621. Each hydrophobic coating layer 624 cancomprise, and/or can consist essentially of, a self-assembly polymermaterial having a hydrophobic functional group that is physicallyexposed to the first sealed chamber 109.

In an alternative embodiment, the at least one vertically-extendingtrench 69 may be formed in the cap structure 700, and may verticallyextend through the first capping surface overlying the first sealedchamber 109. In such an embodiment, each vertically-extending outgassingmaterial portion (comprising an outgassing material layer 622) within anoutgassing-material-containing portion 62 can be formed in the capstructure 700, and can be attached to a portion of the cap structure 700that faces the matrix layer 10 through a respective glue material layer621. Each hydrophobic coating layer 624 can comprise, and/or can consistessentially of, a self-assembly polymer material having a hydrophobicfunctional group that is physically exposed to the first sealed chamber109.

With reference to the embodiments illustrated in FIGS. 8A and 8B, byproviding multiple layers to the outgassing film, such as thehydrophobic coating layer 624, risk of stiction of the movable elements10 a, 10 b may be reduced.

Referring to FIGS. 9A and 9B, a sixth exemplary MEMS device 300 can bederived from any of the preceding exemplary MEMS devices 300 of thepresent disclosure by forming at least one encapsulatedvertically-extending cavity 169′ that are spaced apart from the firstsealed chamber 109 and at least one vertically-extending cavity 69′ thatis a portion of a first sealed chamber 109. For example, the at leastone encapsulated vertically-extending cavity 169′ may be disconnectedfrom the first sealed chamber 109 by a region of anoutgassing-material-containing portion 62 located at the opening of arespective vertically-extending trench 69, and the at least onevertically-extending cavity 69′ can be connected to the first headvolume of the first sealed chamber 109 by the opening of a respectivevertically-extending trench 69.

Referring to FIG. 10, seventh exemplary MEMS device 300 in accordancewith the seventh embodiment of the present disclosure is illustrated. Inthis embodiment, an anisotropic etch process such as a reactive ion etchprocess. Each outgassing-material-containing portion 62 can be formed asa sidewall spacer. A bottom surface of each vertically-extending trench69 may be physically exposed after the anisotropic etch process. Theoutgassing-material-containing portion(s) 62 can include any materialcomposition and/or any layer stack described above.

Vertically-extending surfaces of the outgassing-material-containingportions 62 can be physically exposed to vertically-extending cavities69′ that are portions of the first sealed chamber 109. Bottom surfacesof each vertically-extending trench 69 can be physically exposed to thefirst sealed chamber 109. The bottom surfaces of thevertically-extending trenches 69 may be surfaces of theinterconnect-level dielectric material layers 20 or surfaces of the MEMSsubstrate 50 in embodiments in which the vertically-extending trenches69 extend into the MEMS substrate 50, or may be surfaces of the capstructure 700 in embodiments in which the vertically-extending cavities69 are formed into the cap structure 700.

Referring FIG. 11, an exemplary structure for forming a MEMS assembly inaccordance with a eighth embodiment of the present disclosure isprovided, which can be provided from the exemplary structure of FIG. 1Fby omitting the processing steps of FIGS. 1F, 1G, and 1H, and byperforming the processing steps of FIGS. 1I, 1J and 1K. In other words,the vertically-extending trenches 69 and theoutgassing-material-containing portions 62 are not formed into the MEMSsupport structure 500.

Referring to FIG. 12A, a cap structure 700 in accordance with the eighthembodiment of the present disclosure is illustrated after formation of abonding material layer 72 on a top surface of a cap substrate 70. Theexemplary structure of FIG. 12A can be the same as the exemplarystructure of FIG. 2A.

Referring to FIG. 12B, a photoresist layer (not shown) can be appliedover the bonding material layer 72, and can be lithographicallypatterned to form at least one opening within the area of the firstdevice region 201. An anisotropic etch process can be performed usingthe patterned photoresist layer to form vertically-extending trenches69. The vertically extending trenches 69 can vertically extend throughan upper portion of the cap structure 700. Each vertically-extendingtrench 69 can have a bottom surface within the cap structure 700. The atleast one vertically-extending trench 69 can include a plurality ofvertically-extending trenches 69.

Each vertically-extending trench 69 can have a respective width w at atopmost portion, i.e., at a periphery that adjoins the top surface ofthe matrix layer 10. The width w can be measured between top edges ofopposing segments of the sidewalls for each vertically-extending trench69 that face each other. The width w may be uniform throughout avertically-extending trench 69, for example, for a vertically-extendingtrench 69 having a rectangular opening or for a vertically-extendingtrench having an inner sidewall and an outer sidewall located on arespective arc of two concentric circles having different radii.Alternatively, one or more of the at least one vertically-extendingtrench 69 can have a width modulation. For example, the maximum width ofa vertically-extending trench 69 having a width modulation may be thewidth w, and the vertically-extending trench 69 can include at least oneregion having a lesser width than the width w.

Further, each vertically-extending trench 69 can have a respective depthd between a top periphery and a bottom surface. For eachvertically-extending trench 69, the depth d can be at least twice thewidth w. In one embodiment, the aspect ratio of eachvertically-extending trench 69, i.e., the ratio of the depth d to thewidth w, can be in a range from 2 to 40, such as from 3 to 10. In oneembodiment, each vertically-extending trench 69 can have straightsidewalls. In such an embodiment, the straight sidewalls of eachvertically-extending trench 69 may be vertical, or may have a taperangle greater than 0 degree and less than 45 degrees, such as between 0degree and 10 degrees. Alternatively, the sidewalls of thevertically-extending trench 69 may be convex or concave with a generallydecreasing width with an increasing distance from the horizontal planeincluding the top surface of the cap structure 700. In an non-limitingillustrative example, each vertically-extending trench 69 can have awidth w in a range from 150 nm to 5,000 nm, and a depth in a range from300 nm to 10,000 nm, although lesser and greater dimensions can also beused.

Referring to FIG. 12C, an outgassing-material-containing layer 62L canbe deposited in each vertically-extending trench 69 and over the topsurface of the bonding dielectric layer 72. Theoutgassing-material-containing layer 62L includes at least onecontinuous layer that contains an outgassing material that is hereinreferred to as at least one continuous outgassing material layer. Theoutgassing-material-containing layer 62L may consist of the at least onecontinuous outgassing material layer in some embodiments, or may includeat least one additional material layer in some other embodiments to besubsequently described. In one embodiment, theoutgassing-material-containing layer 62L may consist of a singlecontinuous outgassing material layer or a stack of multiple continuousoutgassing material layers.

Each continuous outgassing material layer within theoutgassing-material-containing layer 62L includes an outgassing materialthat is capable of outgassing at a temperature above room temperature.Any outgassing material or a layer stack including an outgassingmaterial described above may be used to form theoutgassing-material-containing layer 62L. The lateral thickness t ofeach vertical portion of the outgassing-material-containing layer 62L atan opening of a respective vertically-extending trench 69 is less thanone half of the width w of the respective vertically-extending trench69. For example, the lateral thickness t of each vertical portion of theoutgassing-material-containing layer 62L can be in a range from 50 nm to2,500 nm, although lesser and greater lateral thicknesses can also beused. Generally, the lateral thickness t of each vertical portion of theoutgassing-material-containing layer 62L may be thick enough to containa significant amount of the outgassing material (e.g., by being greaterthan 50 nm), and may be thin enough to enable deposition by commerciallyavailable film deposition techniques such as chemical vapor deposition(e.g., by being less than 2,500 nm). A vertically-extending cavity 69′is present within a center region of each vertically-extending trench69. Thus, each vertically-extending portion of theoutgassing-material-containing layer 62L can be physically exposed to arespective vertically-extending trench 69. Each physically exposedsurface of a vertically-extending portion of theoutgassing-material-containing layer 62L can include avertically-extending surface, i.e., a surface that extends along avertical direction, and may have a straight sidewall, a concavesidewall, or a convex sidewall. If a physically exposed surface of avertically-extending portion of the outgassing-material-containing layer62L has a straight sidewall, the straight sidewall may be vertical ortapered.

Referring to FIG. 12D, the horizontal portion of theoutgassing-material-containing layer 62L that overlies the horizontalsurface including the top surface of the bonding dielectric layer 72 canbe removed by a planarization process. For example, a chemicalmechanical planarization (CMP) process can be performed to remove thehorizontal portion of the outgassing-material-containing layer 62L thatoverlies the horizontal surface including the top surface of the bondingdielectric layer 72. Each remaining portion of theoutgassing-material-containing layer 62L located within a respectivevertically-extending trench 69 constitutes anoutgassing-material-containing portion 62.

Generally, a horizontal portion of a continuous outgassing materiallayer within the outgassing-material-containing layer 62L is removedoutside the region including the at least one vertically-extendingtrench 69. The horizontal portion of a continuous outgassing materiallayer within the outgassing-material-containing layer 62L can be removedby chemical mechanical planarization process, an anisotropic etchprocess that does not use any etch mask layer, or an anisotropic etchprocess that uses an etch mask layer (such as a patterned photoresistlayer) that covers the region including the at least onevertically-extending trench 69. Thus, the outgassing-material-containinglayer 62L may be entirely removed from above the horizontal planeincluding the top surface of the bonding dielectric layer 72, or onlyoutside the area that is not covered by the etch mask layer. If an etchmask layer is used, the etch mask layer can continuously extend over theentire area of the at least one vertically-extending trench 69.

Each outgassing-material-containing portion 62 can include avertically-extending outgassing material portion having avertically-extending surface. Each vertically-extending surface of theoutgassing-material-containing portions 62 may have a straight sidewall,a concave sidewall, or a convex sidewall. If anoutgassing-material-containing portion 62 has a straight sidewall, thestraight sidewall may be vertical or tapered. Each vertically-extendingsurface of the vertically-extending outgassing material portion can bephysically exposed a respective vertically-extending cavity 69′ that islocated in a respective vertically-extending trench 69.

Referring to FIG. 12E, the top surface of the cap structure 700 can bepatterned using at least one combination of a lithographic patterningprocess and an etch process. In each lithographic patterning process, aphotoresist layer is applied over a top surface of the cap structure,and is lithographically exposed and developed to form a patternedphotoresist layer that functions as an etch mask layer. In each etchprocess, unmasked surface portions of the cap structure 700 and theoutgassing-material-containing portions 62 are vertically recessed usingthe patterned photoresist layer as an etch mask layer. The etch processcan include an anisotropic etch process (such as a reactive ion etchprocess). The duration of the etch process can be selected to controlthe depth of the recesses formed by the etch process. The photoresistlayer can be removed after the etch process.

A first recess region 177 having a first recessed surface can be formedin the first device region 201, and a second recess region 277 having asecond recessed surface can be formed in the second device region 202.The first recessed surface is subsequently used as a first cappingsurface for the first movable element 10 a, and the second recessedsurface is subsequently used as a second capping surface for the secondmovable element 10 b. Multiple combination of a lithographic patterningprocess and an etch process can be performed to provide various recessedsurfaces having different depth across various device regions. Forexample, a recessed surface in the first device region 201 may have adifferent recess depth than a recessed surface in the second deviceregion 202. Further, at least one of the recessed surfaces may havesteps to provide a pattern in a respective recessed surface. The patternand the depth of each recessed surface can be optimized for each MEMSdevice to be formed in the various device regions. The depths of therecessed surfaces, as measured from the top surface of the bondingmaterial layer 72, may be in a range from 50 nm to 1 micron, althoughlesser and greater depths can also be used.

An upper periphery of each vertically-extending outer sidewall of theoutgassing-material-containing portion 62 can be adjoined to a samehorizontal surface, which is herein referred to as a horizontalreference surface. In one embodiment, the horizontal reference surfacecan be a recessed horizontal surface (i.e., a first capping surface) ofthe cap structure 700.

In one embodiment, each vertically-extending outgassing material portion62 located inside a respective one of the at least onevertically-extending trench 69 can have an outer sidewall that adjoins ahorizontal reference surface that is a horizontal surface of the capstructure 700. In one embodiment, each vertically-extending outgassingmaterial portion of the outgassing-material-containing portion 62 canhave a vertical extent that is greater than a lateral dimension, such asthe width w, of the respective one of the at least onevertically-extending trench 69 at a level of the reference horizontalplane. In one embodiment, each vertically-extending outgassing materialportion of the outgassing-material-containing portion 62 can have alateral thickness t that is less than one half of the lateral dimension,such as the width w, of the respective one of the at least onevertically-extending trench 69.

Referring to FIG. 13, the exemplary structure of FIG. 12E may be bondedto the MEMS assembly of FIG. 11 to form a eighth exemplary MEMS device300. Any of the bonding methods described above may be used to bond thecap structure 700 to the MEMS assembly.

A first sealed chamber 109 including a first movable element 10 a may beformed by aligning the first recess region of the cap structure 700 overthe first movable element 10 a during bonding the cap structure 700 tothe matrix layer 10. The first sealed chamber 109 includes a first headvolume that overlies the first movable element 10 a, and the secondsealed chamber 209 includes a second head volume that overlies thesecond movable element 10 b. The first sealed chamber 109 may belaterally bounded by the matrix layer 10 and may be vertically boundedby the first capping surface that overlies the first movable element 10a. A first MEMS device 100 includes the first movable element 10 a, thefirst sealed chamber 109, and the first capping surface. The first MEMSdevice 100 may form an accelerometer.

A second sealed chamber 209 including a second movable element 10 b maybe formed by aligning the second recess region of the cap structure 700over the second movable element 10 b during bonding the cap structure700 to the matrix layer 10. The second sealed chamber 209 may include asecond head volume that overlies the second movable element 10 b. Thesecond sealed chamber 209 may be vertically bounded by a second cappingsurface that overlies the second movable element 10 b. The secondcapping surface can comprise the planar horizontal surface of the capstructure 700 located within the second recess region. The second sealedchamber 209 may be vertically bounded by the second capping surface thatoverlies the second movable element 10 b. A second MEMS device 200 mayinclude the second movable element 10 b, the second sealed chamber 209,and the second capping surface. The MEMS device of the presentdisclosure can be a composite MEMS device including the first MEMSdevice 100 (which can include an accelerometer) and the second MEMSdevice 200 (which can include a gyroscope).

The outgassing-material-containing portions 62 can include anyoutgassing material or a layer stack including an outgassing materialdescribed above. In one embodiment, each respective vertically-extendingoutgassing material portion of the outgassing-material-containingportions 62 may be located entirely within a volume of a respectivevertically-extending trench 69. In some embodiments, eachvertically-extending outgassing material portion can contact arespective adhesion promotion material layer 623 which contacts arespective hydrophobic coating layer 624. In some embodiments, eachvertically-extending outgassing material portion is attached to theportion of the cap structure 700 that faces the matrix layer 10 througha respective glue material layer 621. In some embodiments, eachhydrophobic coating layer 624 comprises a self-assembly polymer materialhaving a hydrophobic functional group that is physically exposed to thefirst sealed chamber 109.

Referring to FIG. 14, a flow chart 1400 illustrating a set of processingsteps is illustrated. The set of processing steps may be performed toform a MEMS device according to embodiments of the present disclosure.

At step 1410, a MEMS support structure 500 and a cap structure 700 canbe provided. At step 1420, at least one vertically-extending trench 69can be formed in the MEMS support structure 500 or the cap structure700. At step 1430, a vertically-extending outgassing material portion(which can be provided within a respectiveoutgassing-material-containing portion 62) having a surface that isphysically exposed a respective vertically-extending cavity 69′ (i.e, incontact with the respective vertically-extending cavity 69′) can beformed in each of the at least one vertically-extending trench 69. Atstep 1440, a matrix material layer 10L can be attached to the MEMSsupport structure 500, for example, by bonding the matrix material layer10L and optionally thinning the matrix material layer 10L to form athinned matrix material layer 10T. At step 1450, a first movable element10 a laterally confined within a matrix layer 10 can be formed bypatterning the matrix material layer 10L (or the thinned matrix materiallayer 10T). At step 1460, the matrix layer 10 can be bonded to the capstructure 700. A first sealed chamber 109 containing the first movableelement 10 a is formed. Each vertically-extending outgassing materialportion has a surface that is physically exposed to the first sealedchamber 109, which may include a vertically-extending surface exposed toa vertically-extending cavity 69′ and/or a horizontal surface of aoutgassing-material-containing portion 62 exposed to avertically-extending cavity 69′ or including an encapsulatedvertically-extending cavity 169′.

The various embodiments disclosed herein provide an outgassing film 62that covers the sidewalls of vertically-extending cavities 69, whereinthe vertically-extending cavity 69 may be formed in the MEMS supportstructure 500 or in the cap structure 700. Typically, a well in a sealedchamber (e.g., 109, 209) may be filled with an outgassing film. In suchconfigurations, the outgassing film may only outgas from a top surface.By forming the outgassing film 62 on the sidewalls of thevertically-extending cavities 69, but not completely filling thevertically-extending cavities 69, the surface area of the outgassingfilm 62, may be increased. As a result, an increase of outgas may beprovided into a sealed chamber (such as the first sealed chamber 109) toincrease the pressure inside the sealed chamber (such as the firstsealed chamber 109). In many instances, the amount of outgas providedmay be proportional to the exposed surface area of the outgassing film.In some embodiments, the vertically-extending cavity 69 depth may begreater than the thickness of the outgassing film, but smaller than thethickness of a substrate (such as the MEMS support structure 500 or thecap structure 700). In some embodiments, the outgassing film 62 maycomprise a stack of multiple films (621, 622, 623, 624) to increaseoutgas and provide additional functionality. For example, when a topfilm (i.e., the hydrophobic coating layer 624) is hydrophobic, theoutgassing film 62 may provide outgas pressure, but may also reduce thepossibility of stiction. Thus, the various embodiments disclosed hereinmay provide an increase in outgas pressure in the sealed chamber 109while utilizing the same foot-print on the substrate as was utilized ina conventional approach. Thus, when only a small are may be provided toplace outgassing film, the various embodiments disclosed herein mayfurther increase the depth and surface area of the outgassing film 62 toprovide an increase in the quantity of the outgassed gases.

The various embodiments of the present disclosure may provide moreoutgassing material per area than prior art outgassing materialstructures by using at least one vertically-extending trench 69 in whichmore outgassing material can be deposited. Release of gas to a sealedchamber including a movable element can be effected by providing avertically-extending surface of the outgassing material in the at leastone vertically-extending trench 69 such that the vertically-extendingsurface is physically exposed to a vertically-extending cavity 69′ thatis a portion of a sealed chamber containing the movable element,although an encapsulated vertically extending cavity 169′ may be formedinstead and a different surface of the outgassing material may be usedto release gas into the sealed chamber. More amount of the outgassingmaterial per area can provide higher chamber pressure in a sealedchamber for a MEMS device compared to prior art MEMS devices. Further,different MEMS devices may be provided with different numbers ofvertically-extending cavities 69 to optimize the operating pressure ofeach sealed chamber located in the different MEMS devices.

According to an embodiment of the present disclosure, a micro-electromechanical system (MEMS) device is provided, which comprises a MEMSsupport structure 500 bonded to a cap structure 700 through a matrixlayer 10; a first movable element 10 a located inside a first sealedchamber 109 that is laterally bounded by the matrix layer 10; at leastone vertically-extending trench 69 that extends into the MEMS supportstructure 500 or a portion of the cap structure 700 that faces thematrix layer 10, and includes a respective vertically-extendingoutgassing material portion (as contained in a respectiveoutgassing-material-containing portion 62 having a surface in contactwith (and thus, physically exposed to) a respective vertically-extendingcavity (69′ and/or 169′), wherein each vertically-extending outgassingmaterial portion has a surface that is physically exposed to the firstsealed chamber 109.

According to an embodiment of the present disclosure, a semiconductorchip is provided, which comprises: a MEMS support structure 500 bondedto a cap structure 700 through a matrix layer 10; a MEMS device 100including a first movable element 10 a located inside a first sealedchamber 109 that is laterally bounded by the matrix layer 10; asemiconductor circuit located in one of the MEMS support structure 500and the cap structure 700 and configured to sense or control the MEMSdevice 100; at least one vertically-extending trench 69 that extendsinto the MEMS support structure 500 or a portion of the cap structure700 that faces the matrix layer 10, and includes a respectivevertically-extending outgassing material portion having a surface incontact with a respective vertically-extending cavity 69.

According to yet another aspect of the present disclosure, a method offorming a micro-electro mechanical system (MEMS) device is provided. AMEMS support structure 500 and a cap structure 700 may be provided toform at least one MEMS device. At least one vertically-extending trench69 may be formed into the MEMS support structure 500 or a portion of thecap structure 700. A vertical-extending outgassing material portion 62may be formed within the at least one vertically-extending trench 69.The vertical-extending outgassing material portion 62 may have a surfacethat is physically exposed to a respective vertically-extending cavityin each of the at least one vertically-extending trench. A matrixmaterial layer 10L may be attached the MEMS support structure 500. Afirst movable element 10 a laterally surrounded by a matrix layer 10 maybe formed by patterning the matrix material layer 10L (or the thinnedmatrix material layer 10T). The matrix material layer 10L may be bondedto the cap structure 700 such that a first sealed chamber 109 containingthe first movable element is formed. When bonded, eachvertically-extending outgassing material portion 62 has a surface thatis physically exposed to the first sealed chamber 109.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A micro-electro mechanical system (MEMS) device,comprising: a MEMS support structure bonded to a cap structure through amatrix layer; a first movable element located inside a first sealedchamber that is laterally bounded by the matrix layer; avertically-extending trench that extends into the MEMS support structureor a portion of the cap structure that faces the matrix layer; and avertically-extending outgassing material portion located within thevertically-extending trench and having a vertically-extending surfacesthat is exposed to a vertically-extending cavity that adjoins the firstsealed chamber.
 2. The MEMS device of claim 1, further comprising:dielectric material layers located within the MEMS support structure;and metal interconnect structures located in the dielectric materiallayers, wherein the vertically-extending trench extends into at leastone of the dielectric material layers.
 3. The MEMS device of claim 1,wherein: the MEMS support structure comprises a MEMS substrate; and thevertically-extending trench vertically extends into an upper portion ofthe MEMS substrate.
 4. The MEMS device of claim 1, wherein: the firstsealed chamber is bounded by a horizontal capping surface of the portionof the cap structure that faces the matrix layer; and thevertically-extending trench extends into the portion of the capstructure that faces the matrix layer and has a respective peripherythat adjoins the horizontal capping surface.
 5. The MEMS device of claim1, wherein the vertically-extending outgassing material portion islocated entirely within a volume of the vertically-extending trench. 6.The MEMS device of claim 1, wherein the vertically-extending outgassingmaterial portion comprises a portion of anoutgassing-material-containing layer that includes ahorizontally-extending portion contacting a horizontal surface of theMEMS support structure or a horizontal surface of the portion of the capstructure that faces the matrix layer.
 7. The MEMS device of claim 1,wherein the vertically-extending outgassing material portion comprises asilicon oxide material including gases therein, or a material selectedfrom polyimide, poly (para-xylylene) derivatives, and organic compounds.8. A micro-electro mechanical system (MEMS) device, comprising: a MEMSsupport structure bonded to a cap structure through a matrix layer; afirst movable element located inside a first sealed chamber that islaterally bounded by the matrix layer; a vertically-extending trenchthat extends into the MEMS support structure or a portion of the capstructure that faces the matrix layer; and anoutgassing-material-containing portion including a layer stackcomprising an outgassing material layer and a hydrophobic coating layer,located within the vertically-extending trench, and having a surfacethat is physically exposed to the first sealed chamber.
 9. The MEMSdevice of claim 8, wherein the layer stack further comprises an adhesionpromotion material layer located between the outgassing material layerand the hydrophobic coating layer.
 10. The MEMS device of claim 9,wherein the adhesion promotion material layer comprises a silicon oxidematerial having a different material composition than the outgassingmaterial layer, and has a thickness in a range from 1 nm to 20 nm. 11.The MEMS device of claim 8, wherein the hydrophobic coating layer isexposed to a vertically-extending cavity that adjoins the first sealedchamber and is located within the vertically-extending trench.
 12. TheMEMS device of claim 8, wherein the layer stack further comprises a gluematerial layer located between a sidewall of the vertically-extendingtrench and the outgassing material layer.
 13. The MEMS device of claim12, wherein the glue material layer comprises a silicon oxide materialincluding less gas therein than the outgassing material layer, and has athickness in a range from 10 nm to 60 nm.
 14. The MEMS device of claim8, wherein the hydrophobic coating layer comprises a self-assemblypolymer material having a hydrophobic functional group that isphysically exposed to the first sealed chamber.
 15. The MEMS device ofclaim 14, wherein the self-assembly polymer material comprises amaterial selected from CF3(CF2)5(CH2)2SiCl3, CF3(CF2)5(CH2)2Si(OC2H5)3,CF3(CF2)5(CH2)2Si(CH3)Cl2, CF3(CF2)5(CH2)2Si(CH3)2Cl,CF3(CF2)7(CH2)2SiCl3 (FDTS), and CH3(CH2)17(CH2)2SiCl3 (OTS).
 16. Amicro-electro mechanical system (MEMS) device, comprising: a MEMSsupport structure bonded to a cap structure through a matrix layer; afirst movable element located inside a first sealed chamber that islaterally bounded by the matrix layer; a vertically-extending trenchthat extends into the MEMS support structure or into the cap structure;and a vertically-extending outgassing material portion located withinthe vertically-extending trench, having a surface that is physicallyexposed to the first sealed chamber, and having a lateral thickness thatis less than one half of a width of the vertically-extending trench. 17.The MEMS device of claim 16, wherein: the MEMS support structurecomprises multiple dielectric material layers located between a MEMSsubstrate and the first sealed chamber; and the vertically extendingtrench extends into at least two dielectric material layers among themultiple dielectric material layers.
 18. The MEMS device of claim 17,further comprising metal line structures and metal via structureslocated at different metal interconnect levels and embedded in themultiple dielectric material layers, wherein the vertically-extendingtrench vertically extends through at least two different levels of themetal line structures and at least two different levels of the metal viastructures.
 19. The MEMS device of claim 18, wherein a bottom surface ofthe vertically-extending trench is more proximal to the MEMS substratethan any metal interconnect structure located in the at least twodifferent levels of the metal line structures or in the at least twodifferent levels of the metal via structures.
 20. The MEMS device ofclaim 16, wherein: the vertically extending trench extends into the MEMSsupport structure; and a horizontally-extending outgassing materialportion is adjoined to the vertically-extending outgassing materialportion, and has a horizontal surface that is exposed to the firstsealed chamber, the horizontal surface being more proximal to the capstructure than the vertically-extending outgassing material portion isto the cap structure.